1. Field of the Invention
The present invention relates to a bending portion including a bending piece set that includes a plurality of bending pieces formed by cutting a rigid pipe and is configured by pivotably coupling adjacent bending pieces to each other.
2. Description of the Related Art
Endoscopes applicable to industrial use and medical use are each provided with an insertion portion to be inserted into a living body or a tube. In general, in such an endoscope including a flexible insertion portion, a bending portion is provided on a distal end side of the insertion portion. The bending portion performs a bending action along with an operation of an operation apparatus provided to an operation portion. Accordingly, in the endoscope including the bending portion, the operation apparatus enables an observation portion provided in a distal end portion to face in a desired direction.
The bending portion is provided with a bending piece set. The bending piece set is configured by pivotably coupling a plurality of bending pieces to each other such that the bending piece set is bent at a predetermined angle in a predetermined direction. In general, the plurality of bending pieces constituting the bending piece set are pivotably coupled to each other by pivot pins.
Japanese Patent Application Laid-Open Publication No. 09-117413 discloses an inflectable tube as a barrel for a flexible endoscope that can be simply and economically made, and also discloses a manufacturing method therefor. The inflectable tube (corresponding to a bending portion set in the invention of the present application) is formed by laser-cutting a rigid tube. As illustrated in FIG. 1A (corresponding to FIG. 4 in Japanese Patent Application Laid-Open Publication No. 09-117413), adjacent tube part 2a (indicated by solid lines) and tube part 2b (indicated by broken lines) of an inflectable tube 1 formed by laser-cutting are separated from each other by a circumferential separation joint in terms of a material. On the other hand, the adjacent tube part 2a and tube part 2b of the inflectable tube 1 are reliably connected to each other by an engagement portion 3 formed by the separation joint.
Then, the tube parts 2a, 2b of the inflectable tube 1 pivot with respect to each other about the engagement portion 3 including a circular convex portion 3b and a circular concave portion 3c, so that the tube part 2b is inflected by θ1 with respect to the tube part 2a, for example, as indicated by chain double-dashed lines (corresponding to FIG. 6 in Japanese Patent Application Laid-Open Publication No. 09-117413). In the figure, the tube part 2a and the tube part 2b have the same shape.
Note that, in the present embodiment, the inflectable tube is also described as bending portion set, and each tube part is also described as bending piece.
There is a significant difference in tensile strength between: the bending portion set in which the adjacent bending pieces are connected to each other by the engagement portion as described above; and the bending portion set in which the adjacent bending pieces are coupled to each other by the pivot pins such as rivets as described above. More specifically, the bending portion set in which the bending pieces are coupled to each other by the pivot pins is higher in tensile strength than the bending portion set in which the bending pieces are connected to each other by the engagement portion.
For this reason, the bending portion including the bending portion set in which the bending pieces are coupled to each other by the pivot pins is higher in resistance to tensile stress. Accordingly, a technique of pulling a sigmoid colon or a transverse colon closer by means of the insertion portion inserted in a large intestine can be easily performed. Moreover, when the insertion portion is cleaned and disinfected, the bending portion is drawn through an operator's hand in an insertion direction, whereby the cleaning work can be easily performed.
Moreover, in the endoscope including the bending portion in the insertion portion, the bending portion is required to be capable of turning in a small circle, in addition to a reduction in diameter of the insertion portion. The bending portion capable of turning in a small circle refers to a bending portion having a small bending radius at the time of bending and having a small length. In the endoscope including the bending portion capable of turning in a small circle, if a bending action of the bending portion is performed with a forward region in the insertion direction being observed, for example, observation up to a rearward region in the insertion direction is possible.
In the bending portion set in Japanese Patent Application Laid-Open Publication No. 09-117413, as illustrated in FIG. 1B, an inflection angle between neighboring bending pieces 2Aa, 2Ab constituting a bending portion set 1A is set to an angle θ2 larger than the angle θ1 illustrated in FIG. 1A. For this reason, in each bending piece 2A in FIG. 1B, an end face position of a first escape portion 4 and an end face position of a second escape portion 5 that are provided to each bending piece 2 in FIG. 1A are respectively changed from first positions 4a, 5a to second positions 4b, 5b. As a result, as illustrated in FIG. 2, a bending radius of the bending portion set 1A is smaller than a bending radius of the bending portion set 1.
Moreover, in a bending portion set 1B illustrated in FIG. 1C, a distance between pivot axes of neighboring bending pieces 2Ba, 2Bb is set to a length L2 smaller than a length L1 illustrated in FIG. 1A. For this reason, each bending piece 2B of the bending portion set 1B corresponds to one formed by omitting, for example, middle parts 6a, 6b that are indicated by hatched lines in the bending piece 2 constituting the bending portion set 1. As a result, as illustrated in FIG. 2, a bending radius of the bending portion set 1B is smaller than the bending radius of the bending portion set 1.
Further, a bending portion set 1C is configured such that a distance between pivot axes of neighboring bending pieces 2Ca, 2Cb is set to L2 and that the neighboring bending pieces 2Ca, 2Cb pivot with respect to each other at the angle θ2 as illustrated in FIG. 1D. Consequently, a length of the bending piece set can be made smaller, and, as illustrated in FIG. 2, a bending radius of the bending portion set 1C is smaller than the bending radii of the bending portion sets 1, 1A, 1B.
In the bending portion sets 1, 1A, 1B, 1C in each of which the bending pieces are connected to each other by the engagement portion, as illustrated in FIG. 3, the engagement portion 3 including the circular convex portion 3b and the circular concave portion 3c is configured by a separation joint 9 formed by a laser beam. The separation joint 9 is formed by the laser beam that is applied from an outer circumferential face side of a rigid pipe 8 toward a central axis 8a of the pipe 8. For this reason, in the engagement portion 3, a convex-portion tapered surface 3Tb formed in a periphery of the circular convex portion 3b is put on a concave-portion tapered surface 3Tc formed in an inner circumference of the circular concave portion 3c. 